Aqueous polymer dispersions

ABSTRACT

The overall performance of water-reducible polymer dispersions, more specifically alkyd dispersions, can be substantially improved by utilizing resins derived from acidolysis reaction products of polyalkylene terephthalates and polyalkylene naphthalates. According to this invention, polymer dispersions can be produced from low acid value polymers and yet have good water dispersibility. When an aqueous coating composition is formulated using the dispersion of this invention, a final coating is formed that has good hydrolytic stability, and when blended with a latex, exhibits improved gloss and wet adhesion.

This application claims the benefit of U.S. provisional patentapplication No. 60/183,311 filed Feb. 17, 2000.

BACKGROUND OF THE INVENTION

This invention relates to an aqueous polymer dispersion having a lowacid value and low volatile organic level utilizing a polyalkyleneterephthalate, or polyalkylene naphthalate, as a raw material forproducing the resin. The process for making the dispersion includes anacidolysis reaction of polyalkylene terephthalate, or polyalkylenenaphthalate, to produce a low acid value resin, and subsequentlyperforming a monomer modification of the resin followed by combining themodified resin with water in the presence of a base to provide waterdispersibility. More specifically, the aqueous dispersion of thisinvention can be an alkyd dispersion.

It has been known to employ water-reducible alkyds as binders to replacesolventborne alkyds in order to reduce volatile organic content (VOC).One way to disperse an alkyd in water is to synthesize a high acid valuealkyd in a water miscible solvent followed by neutralization andaddition of water. Such alkyd resins and film-forming systems basedthereon, however, have the disadvantages of unsatisfactory resistance towater, poor hydrolytic stability, and require considerable amounts ofvolatile amines and solvents for satisfactory dispersion. Another way todisperse an alkyd in water is to emulsify the alkyd in the presence oflarge amounts of surface-active agents. However, surface-active agentstend to impair the moisture resistance of the resulting coatings. Theaqueous coating compositions produced utilizing the dispersions of thisinvention exhibit good hydrolytic stability and moisture resistance.

Water-reducible alkyds have also been used in aqueous coatingcompositions to improve the properties of latex coatings. In manyinstances, high gloss and wet adhesion have been difficult to achievewith latex coatings. Current water-reducible alkyds, such as thosedescribed above, when blended with a latex, may improve wet adhesion andgloss, but negatively impact stability or moisture resistance. Theaqueous coating compositions produced utilizing the dispersions of thisinvention as a secondary binder with latex exhibit improved gloss andadhesion properties compared to unmodified latex coatings. These paintsalso exhibit improved stability and moisture resistance as compared tocurrent water-reducible alkyd modified latex paints.

It has now been found that the overall performance of water-reduciblepolymer dispersions, more specifically alkyd dispersions, can besubstantially improved by utilizing resins derived from acidolysisreaction products of polyalkylene terephthalates and polyalkylenenaphthalates. According to this invention, polymer dispersions can beproduced from low acid value polymers and yet have good waterdispersibility. When an aqueous coating composition is formulated usingthe dispersion of this invention, a final coating is formed that hasgood hydrolytic stability, and when blended with a latex, exhibitsimproved gloss and wet adhesion.

SUMMARY OF THE INVENTION

It is an object of this invention to provide an aqueous polymerdispersion useful for aqueous coating compositions, comprising:

-   -   a. a low acid value polymer formed by the reaction product of        -   (1) a mixture of compounds resulting from an acidolysis            reaction of a polyalkylene terephthalate (or naphthalate)            with a member of the group consisting of acid- and            anhydride-functional materials; and        -   (2) an alcohol, wherein the resulting reaction product of            steps (1) and (2) has an acid value of less than 20; and    -   b. an ethylenically-unsaturated monomer suitable for modifying        the low acid value polymer to form a modified polymer resin;        wherein the modified polymer resin has an acid value of less        than 30, and wherein surfactants are optionally present and        wherein said modified polymer resin is subjected to temperatures        higher than its melting point and then combined with water in        the presence of a base with high shear dispersing to form the        aqueous polymer composition.

It is another object of this invention to provide a process forproducing an aqueous polymer dispersion useful for aqueous coatingcompositions, comprising:

-   -   a. producing a low acid value polymer formed by the reaction        product of:        -   (1) a mixture of compounds resulting from an acidolysis            reaction of a polyalkylene terephthalate (or naphthalate)            with a member of the group consisting of acid- and            anhydride-functional materials; and        -   (2) an alcohol, wherein the resulting reaction product of            step (1) and (2) has an acid number of less than 20; and    -   b. performing a monomer modification by reacting an        ethylenically unsaturated monomer with the low acid value        polymer to form a modified polymer resin at a temperature        sufficient to maintain the modified polymer resin in a flowable        molten state, wherein the modified polymer resin has an acid        value of less than 30;    -   c. combining the modified polymer resin with water in the        presence of a base at temperatures sufficient to maintain the        modified polymer resin in a flowable molten state; and    -   d. forming a dispersion of the molten modified polymer resin by        subjecting the modified polymer resin to high shear dispersing;        wherein a non-ionic surfactant is optionally added.

A further object of this invention is to provide an aqueous coatingcomposition utilizing a water-reducible polymer dispersion derived frompolyalkylene terephthalate, or polyalkylene naphthalate, as a solebinder or blended with latex, and the process for producing the aqueouscoating composition. The aqueous coating composition has good hydrolyticstability, and improved gloss and good wet adhesion when blended with alatex.

These and other objects will become more readily apparent from thedetailed description, examples and claims which follow below.

DETAILED DESCRIPTION OF THE INVENTION

This invention relates to novel aqueous dispersions of low acid valuepolymer resins which utilize a polyalkylene terephthalate orpolyalkylene naphthalate as a raw material for producing thedispersions. The coating compositions produced utilizing the dispersionsof this invention have good hydrolytic stability and improved gloss andwet adhesion properties when blended with a latex. This invention alsorelates to a process for producing such coatings.

This invention also relates to novel aqueous coating compositions havingimproved gloss, wet adhesion, and hydrolytic stability comprisingwater-reducible polymer dispersions utilizing polyalkyleneterephthalate, or polyalkylene naphthalate, as the starting material forthe production of the polymer. The preferred polyalkylene terephthalateis polyethylene terephthalate (PET). Polyethylene naphthalate (PEN) canalso be used. Other polyalkylene terephthalates are polypropyleneterephthalate, polybutylene terephthalate, etc. Polymer resindispersions prepared in accordance with this invention are highlysuitable, even without the use of organic solvents, as binders foraqueous coating compositions.

In accordance with the present invention, a polyalkylene terephthalateresin, typically having a structure as shown in FIG. I:

FIG. I:

R=C2–C12 straight chain or branched alkylene;n>1or a polyalkylene naphthalate having a structure as shown in FIG. II:FIG. II:

is first digested into lower molecular weight oligomeric units throughan acidolysis reaction. The digestion product of the acidolysis reactionis then further reacted with a hydroxy-functional reactant to produce aresin which is further monomer-modified and dispersed into water. Forpurposes of this invention, the use of polyethylene terephthalate isdescribed; however, it should be recognized by those skilled in the artthat other polyalkylene terepthalates, or polyalkylene naphthalates, canbe used similarly.

1. PET Source

The actual source of PET usable herein is not of critical importance tothis invention. “Virgin” PET, that is PET which is commercially producedspecifically as a raw material, is acceptable from a chemical standpointfor use herein. Likewise, recycled or reclaimed PET is acceptable from achemical standpoint. At the time of this application, there areadvantages to the environment (reduction of solid waste) and to theeconomics of this process (recycled PET is much less expensive thanvirgin PET) by using recycled or reclaimed PET; and, there are noperformance disadvantages to using recycled PET versus virgin PET.Typically, the sources for PET are many and varied. One source of eithervirgin or recycled PET is material from PET polymer manufacturers.Another source for PET can be post-industrial outlets. A further sourceis reclaimed PET, such as recycled PET beverage bottles. It should beappreciated that any source of PET is acceptable. Polyethylenenaphthalate and polybutylene terephthalate are available similarly.

For purposes of this invention, the PET should be provided in acomminuted form. It can be flaked, granulated, ground to a powder orpelletized. The only constraint placed on the PET at this point is thatit is relatively pure; that is, there should not be a level ofimpurities above about one weight percent (1 wt %) nor should there beany appreciable level of impurities which are chemically reactive withinthis process. Polyols also used in the manufacture of PET includediethylene glycols, triethylene glycols, neopentyl glycol, cyclohexanedimethanol, butanediols, and propanediols are used as polymer modifiers,and are acceptable as used in this invention.

2. Chemistry of PET-Based Polymers

PET is comprised of repeating units of ethylene glycol and terephthalicacid connected by ester linkages. FIG. I, above, shows a typical PETmolecule where R is ethylene. Each repeating unit of PET has a weightaverage molecular weight of 192 with one equivalent of ethylene glycoland one equivalent of terephthalic acid. By reacting PET with an acid,it is possible to reduce the average chain length of the PET molecules.The chemistry of PET is such that an equilibrium exists between PET,water, ethylene glycol (EG), terephthalic acid (TPA), and the acid usedto reduce the chain length. This equilibrium makes it possible tosubstantially reverse the polymerization process and depolymerize PETinto its starting materials.

a. Acidolysis of PET

It is possible to reverse the PET equilibrium and reduce the averagechain length of PET with an acid- or anhydride-functional material. The“acidolysis” of PET comprises the reaction of PET with an acid- oranhydride-functional material.

a.1. Acids for Use in Acidolysis Reaction

Suitable acid-functional materials include mono-functional acids such asbenzoic, crotonic and sorbic acids; and acids having an acidfunctionality on average of at least two, such as phthalic acid,isophthalic acid, 1,4-cyclohexane dicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, succinic acid, adipic acid, azelaic acid, maleicacid, fumaric acid, trimellitic acid, trimesic acid, naphthalenedicarboxylic acids, carboxy-terminated polybutadiene, benzophenonetetracarboxylic dianhydride, 4,4′-dicaboxy diphenoxy ethane, and thehydroxy carboxylic acids of piralactone. Other suitable acids includethe saturated acids such as butyric, caproic, caprylic, capric, lauric,myristic, palmitic, stearic, 12-hydroxystearic, arachidic, behenic andlignoceric acids; the unsaturated acids such as palmitoleic, oleic,ricinoleic, linoleic, linolenic, eleostearic, licaric, gadoleic anderacic acids; and the oils (and their fatty acids) such as canola,rapeseed, castor, dehydrated castor, coconut, coffee, corn, cottonseed,fish, lard, linseed, oticica, palm kernal, peanut, perilla, safflower,soya, sunflower, tallow, tung, walnut, vernonia, tall and menhaden oils;and blends and mixtures of natural and synthetic oils and fatty acids,particularly those oils and fatty acids with high iodine numbers.

a.2. Anhydrides for Use in Acidolysis Reaction

Representative anhydrides include, phthalic anhydride, 3-nitrophthalicanhydride, 4-nitrophthalic anhydride, 3-flourophthalic anhydride,4-chlorophthalic anhydride, tetrachlorophthalic anhydride, tetrabromophthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalicanhydride, methylhexahydrophthalic anhydride, succinic anhydride,dodecenylsuccinic anhydride, octylsuccinic anhydride, maleic anhydride,dichloromaleic anhydride, glutaric anhydride, adipic anhydride,chlorendic anhydride, itaconic anhydride, citraconic anhydride,endo-methylenetetrahydrophthalic anhydride, cyclohexane-1,2-dicarboxylicanhydride, 4-cyclohexene-1,2-dicarboxylic anhydride,4-methyl-4-cyclohexene-1,2-dicarboxylic anhydride,5-norbornene-2,3-dicarboxylic anhydride,1,4-cyclohexadiene-1,2-dicarboxylic anhydride,1,3-cyclopentanedicarboxylic anhydride, diglycolic acid anhydride, andthe like.

Other useful anhydrides include those anhydrides having a free carboxylgroup in addition to the anhydride group such as trimellitic anhydride,aconitic anhydride, 2,6,7-naphthalene tricarboxylic anhydride,1,2,4-butane tricarboxylic anhydride, 1,3,4-cyclopentane tricarboxylicanhydride, and the like.

It should be appreciated that other acids and anhydrides should beconsidered equivalents of those named herein.

The acid- or anhydride functional material will generally have a numberaverage molecular weight below about 2000. Preferably the acid- oranhydride-functional material will have a number average molecularweight of below about 600. Typical number average molecular weights ofthese materials will range from about 96 to about 600.

Especially preferred acids and anhydrides include the vegetable fattyacids described above and isophthalic acid, hexahydrophthalic acid,1,4-cyclohexane dicarboxylic acid, 2,6-naphthalene dicarboxylic acid,and mixtures thereof.

Optionally, a catalyst can be used for the acidolysis reaction. If used,suitable catalysts for acidolysis of PET include the traditionaltransesterification catalysts including stannous octoate, calciumhydroxide, lithium hydroxide, barium hydroxide, sodium hydroxide,lithium methoxide, manganese acetate tetrahydrate, dibutyl tin oxide,butyl stannoic acid, and hydrated monobutyl tin oxide. If used, thecatalyst should be present in an amount of from about 0.1 weight % toabout 1.5 weight % based upon the total weight of the PET andacid-functional material.

When PET and an acid- or anhydride-functional material are reactedtogether in the presence of the catalyst (optional) and heat, the highmolecular weight PET molecule is broken down into shorter chainfragments. This is accomplished through acidolysis of the ester linkagesand exchange by the acid with the terephthalic acid units of the PETmolecule. This exchange continues to occur until a new equilibrium isestablished between the PET, the shorter chain length PET, the shorterchain length PET substituted with the acid, the acid-functional materialand terephthalic acid.

Subsequent to acidolysis, the remaining PET fragments and products inequilibrium therewith are predominantly acid-functional. As describedfurther below, the acidolysis reaction products can be reacted withhydroxy-functional materials and the like to form excellent coatingcompositions. The reaction can be carried out in the presence of asolvent for azeotroping of water or fusion in solventless systems.

b. Further Reactions of the Acidolysis Products

The products of the acidolysis reaction are further reacted withhydroxy-functional materials to produce a polyester product useful incoating compositions. Since the acidolysis reaction products arepredominantly acid-functional, they can be further reacted with alcoholsincluding those taught below to obtain polymer compositions useful incoatings. By controlling the amounts and types of reactants, as well asthe length and temperature of the reaction as discussed below, one canformulate low acid value systems from the acidolysis reaction products.The products of such reactions include alkyds and polyesters which canbe further modified and dispersed in water. The resulting polymercomposition can be used by itself or in combination with latex as afilm-forming resin in coating compositions. Conventional additives, suchas defoamers, UV-stabilizers, pigments, etc. may also be added.

b.1. Alcohols

Generally, the alcohols will have number average molecular weights ofbelow about 4000, and typically, number average molecular weights willrange from about 30 to about 4000, and especially 100 to about 600.Methods of preparing alcohols are well known in the art and the methodof preparation of the alcohols is not critical to the practice of thisinvention.

Suitable alcohols include the C1–C22 linear and branched saturated andunsaturated alcohols including, for example, methanol, ethanol,propanol, butanol, hexanol, linoleyl alcohol, trimethylolpropane diallylether, allyl alcohol, 2-mercaptoethanol and the like. Additionally,useful alcohols include the hydroxy-functional polyethers, polyesters,polyurethanes, polycaprolactones, etc. as generally discussed inSections b.1.a. through b.1.e. below.

-   -   b.1.a. Saturated and unsaturated polyols include glycerol,        castor oil, ethylene glycol, dipropylene glycol, 2,2,4-trimethyl        1,3-pentanediol, neopentyl glycol, 1,2-propanediol,        1,3-propanediol, 1,4-butanediol, 1,3-butanediol, 2,3-butanediol,        1,5-pentanediol, 1,6-hexanediol, 2,2-dimethyl-1,3-propanediol,        Bisphenol A tetraethoxylate, dodecahydro Bisphenol A, 2,2′-thio        diethanol, dimethylol propionic acid, acetylenic diols,        hydroxy-terminated polybutadiene, 1,4-cyclohexanedimethanol,        1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol,        1,4-bis(2-hydroxyethoxy)cyclohexane, trimethylene glycol, tetra        methylene glycol, pentamethylene glycol, hexamethylene glycol,        decamethylene glycol, diethylene glycol, triethylene glycol,        tetraethylene glycol, norbomylene glycol, 1,4-benzenedimethanol,        1,4-benzenediethanol, 2,4-dimethyl-2-ethylenehexane-1,3-diol,        2-butene-1,4-diol, and polyols such as trimethylolethane,        trimethylolpropane, di-trimethylolpropane, trimethylolpropane        monoallyl ether, trimethylolhexane, triethylolpropane,        1,2,4-butanetriol, glycerol, pentaerythritol, dimethylolpropane,        dipentaerythritol, methyl propanediol, phenolic polyols, etc.    -   b.1.b. Polyether polyols are well known in the art and are        conveniently prepared by the reaction of a diol or polyol with        the corresponding alkylene oxide. These materials are        commercially available and may be prepared by a known process        such as, for example, the processes described in Encyclopedia of        Chemical Technology, Volume 7, pages 257–262, published by        Interscience Publishers, Inc., 1951. Representative examples        include the polypropylene ether glycols and polyethylene ether        glycols such as those marketed as NIAX® Polyols from Union        Carbide Corporation.    -   b.1.c. Another useful class of hydroxy-functional polymers are        those prepared by condensation polymerization reaction        techniques as are well known in the art. Representative        condensation polymerization reactions include polyesters        prepared by the condensation of polyhydric alcohols and        polycarboxylic acids or anhydrides, with or without the        inclusion of drying oil, semi-drying oil, or non-drying oil        fatty acids. By adjusting the stoichiometry of the alcohols and        the acids while maintaining an excess of hydroxyl groups,        hydroxy-functional polyesters can be readily produced to provide        a wide range of desired molecular weights and performance        characteristics.

The polyester polyols are derived from one or more aromatic and/oraliphatic polycarboxylic acids, the anhydrides thereof, and one or morealiphatic and/or aromatic polyols. The carboxylic acids include thesaturated and unsaturated polycarboxylic acids and the derivativesthereof, such as maleic acid, fumaric acid, succinic acid, adipic acid,azelaic acid, and dicyclopentadiene dicarboxylic acid. The carboxylicacids also include the aromatic polycarboxylic acids, such as phthalicacid, isophthalic acid, terephthalic acid, etc. Anhydrides such asmaleic anhydride, phthalic anhydride, trimellitic anhydride, or NADICMethyl Anhydride (brand name for methylbicyclo[2.2.1]heptene-2,3-dicarboxylic anhydride isomers) can also beused.

Representative saturated and unsaturated polyols which can be reacted instoichiometric excess with the carboxylic acids to producehydroxy-functional polyesters include the diols taught in b.1.a. andb.1.b., above.

Typically, the reaction between the polyols and the polycarboxylic acidsis conducted at about 120° C. to about 200° C. in the presence of anesterification catalyst such as dibutyl tin oxide.

-   -   b.1.d. Additionally, hydroxy-functional polymers can be prepared        by the ring opening reaction of epoxides and/or polyepoxides        with primary or, preferably, secondary amines or polyamines to        produce hydroxy-functional polymers. Representative amines and        polyamines include ethanol amine, N-methylethanol amine,        dimethyl amine, ethylene diamine, isophorone diamine, etc.        Representative polyepoxides include those prepared by condensing        a polyhydric alcohol or polyhydric phenol with an epihalohydrin,        such as epichlorohydrin, usually under alkaline conditions. Some        of these condensation products are available commercially under        the designations EPON® from Shell Chemical Company, and methods        of preparation are representatively taught in U.S. Pat. Nos.        2,592,560; 2,582,985 and 2,694,694.    -   b.1.e. Other useful hydroxy-functional polymers can be prepared        by the reaction of an excess of at least one alcohol, such as        those representatively described above, with isocyanates to        produce hydroxy-functional urethanes. Representative        mono-functional isocyanates include allyl isocyanate and tolulyl        isocyanate. Representative polyisocyanates include the aliphatic        compounds such as ethylene, trimethylene, tetramethylene,        pentamethylene, hexamethylene, 1,2-propylene, 1,2-butylene,        2,3-butylene, 1,3-butylene, ethylidene and butylidene        diisocyanates; the cycloalkylene compounds such as 3-isocyanato        methyl-3,5,5-trimethyl cyclohexylisocyanate, and the        1,3-cyclopentane, 1,3-cyclohexane, and 1,2-cyclohexane        diisocyanates; the aromatic compounds such as m-phenylene,        p-phenylene, 4,4′-diphenyl, 1,5-naphthalene and 1,4-naphthalene        diisocyanates; the aliphatic-aromatic compounds such as        4,4′-diphenylene methane, 2,4- or 2,6-toluene, 4,4′-toluidine,        and 1,4-xylylene diisocyanates; benzene 1,3-bis        (1-isocyanato-1-methyl ethyl); the nuclear substituted aromatic        compounds such as dianisidine diisocyanate, 4,4′-diphenylether        diisocyanate and chlorodiphenylene diisocyanate; the        triisocyanates such as triphenyl methane-4,4′,4″-triisocyanate,        1,3,5-triisocyanate benzene and 2,4,6-triisocyanate toluene; and        the tetraisocyanates such as 4,4′-diphenyl-dimethyl        methane-2,2′-5,5′-tetraisocyanate; the polymerized        polyisocyanates such as tolylene diisocyanate dimers and        trimers, and other various polyisocyanates containing biuret,        urethane, and/or allophanate linkages. The isocyanates and the        alcohols are typically reacted at temperatures of 25° C. to        about 150° C. to form the hydroxy-functional polymers.

Especially preferred hydroxy-functional materials in the practice ofthis invention include, but are not limited to, ethylene glycol,dipropylene glycol, 2,2,4-trimethyl 1,3-pentanediol, neopentyl glycol,1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,3-butanediol,2,3-butanediol, 1,5-pentanediol, 1,6-hexanediol,2,2-dimethyl-1,3-propanediol, 1,4-cyclohexanedimethanol,1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol,1,4-bis(2-hydroxyethoxy)cyclohexane, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol,decamethylene glycol, diethylene glycol, triethylene glycol,tetraethylene glycol, norbornylene glycol, 1,4-benzenedimethanol,1,4-benzenediethanol, 2,4-dimethyl-2-ethylenehexane-1,3-diol,2-butene-1,4-diol, and polyols such as trimethylolethane,trimethylolpropane, trimethylolpropane monoallyl ether,trimethylolhexane, triethylolpropane, di-trimethylolpropane,1,2,4-butanetriol, glycerol, pentaerythritol, dipentaerythritol, andmixtures thereof.

Most preferred are trimethylolethane, trimethylolpropane,pentaerythritol, dipentaerythritol, and mixtures thereof. It should beappreciated that other alcohols should be considered equivalents ofthose named herein.

c. Low Acid Value Products Using the Acidolysis Reaction Products

As stated above, the acidolysis reaction products can be further reactedwith alcohol to produce low acid value products. The term “low acidvalue products” is meant to be those compositions having acid valueslower than about 20. In order to formulate an acidolysis reactionproduct to a low acid value of less than about 20, the followingstoichiometric proportions of materials should be used. For each mole ofrepeating unit PET used, from about 1.5 to about 4.0 equivalents ofacid/anhydride should be used in the acidolysis reaction, followed byfurther reaction with about 2.0 to about 4.0 equivalents ofhydroxy-functionality. Preferably, the equivalents of acid/anhydride torepeating unit of PET should be about 2.0:1 to about 3.1:1 and theequivalents of OH to PET should be about 2.3:1 to about 3.7:1.Optionally, small amounts of amine or diamine can be substituted forsome of the alcohols.

The low acid value products can be used by themselves, in combinationwith other well known coatings additives, including pigments, flowagents, catalysts, diluents, driers (such as cobalt, zirconium, calciumor organic carboxylates), solvents, ultraviolet light absorbers, and thelike, or can be further mixed, reacted, or modified as described below.

The low acid value products (that is, acid values less than about 20)can be reduced in solvents such as xylene, toluene, mineral spirits andthe like. Such products can then be allowed to air dry or forced to dryby baking as is well known in the art. A melamine-formaldehyde resin,isocyanate, or other crosslinking agent would preferably be added tofacilitate drying in the bake systems. In a preferred embodiment, thelow acid value products can be directly modified with monomers,oligomers and polymers to produce water-reducible polymers. Theresulting low acid value product is hereinafter referred to as a basepolymer.

d. Monomer Modifications of the Base Polymers

In another preferred embodiment, the base polymers of Section (c) can befurther modified by direct monomer modification. Direct monomermodification is typically conducted under conditions also well known inthe art, including the procedures taught in U.S. Pat. Nos. 4,735,995 and4,873,281, incorporated herein by reference, as well as by theprocedures taught in the Examples below.

When monomerically modifying the base polymers, the incorporation of asufficient amount of acid-functional monomer material, with or withoutsurfactants, will enable the final polymer products to be reducible inwater or other aqueous systems when sufficiently neutralized asdiscussed below.

Surfactants that can optionally be used for this invention includenonionic surfactants such as, but not limited to, nonylphenolethoxylates (such as IGEPAL® CO-Series available from Rhodia, Cranberry,N.J.), octylphenol ethoxylates (such as IGEPAL® CA-Series available fromRhodia, Cranberry, N.J.), polyether polyols (such as PLURONIC® orTETRONIC® available from BASF Corporation, Mt. Olive, N.J.), andacetylenic alcohols (such as SURFYNOL® available from Air Products,Allentown, Pa.). The surfactant, if present, is preferably about 1% toabout 5% of the total weight of the polymer.

Generally, amounts of acid-functional monomer materials greater thanabout 5.0% by weight of the total amount of monomer and otherethylenically unsaturated materials will result in a coating compositionwhich is water reducible. Amounts less than the above will generallyresult in coatings which are not water reducible. Preferably, themonomer-modified base polymer of this invention has low volatile organiclevels. More preferably, the volatile organic level of themonomer-modified base polymer is less than 10%.

Suitable monomers for modifying the base polymer include those acrylic,vinylic and ethylenically unsaturated materials taught to be useful whenreacted with unsaturated acids, such as acrylic acid, methacrylic acidand itaconic acid. Suitable vinyl monomers are, for example,alkylacrylates, alkylmethacrylates, hydroxyalkyl acrylates, hydroxyalkylmethacrylates, acrylamides, methacrylamides, vinyl aromatichydrocarbons, vinyl aliphatic hydrocarbons or mixtures thereof. Whileacrylic acid and methacrylic acid are preferred ethylenicallyunsaturated carboxylic acids, other suitable ethylenically unsaturatedcarboxylic acid monomers may be used such as beta-carboxyethylacrylates, itaconic acid, crotonic acid, maleic acid, and half esters ofmaleic and fumaric acids, such as butyl hydrogen maleate and ethylhydrogen fumarate, in which one carboxyl group is esterified with analcohol. Examples of other ethylenically unsaturated monomers which canbe used for making the vinyl polymer include the alkyl acrylates, suchas methyl acrylate, ethyl acrylate, butyl acrylate, propyl acrylate,2-ethylhexyl acrylate and isobornyl acrylate; the alkyl methacrylates,such as methyl methacrylate, butyl methacrylate, 2-ethylhexylmethacrylate, decyl methacrylate, lauryl methacrylate, acetoacetoxyethylmethacrylate, dimethylaminoethyl methacrylate, and allyl methacrylatesand isobornyl methacrylate; hydroxyalkyl acrylates and methacrylatessuch as hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethylmethacrylate, hydroxypropyl methacrylate; acrylamides andmethacrylamides, diacetone acrylamide, and unsaturated nitriles such asacrylonitrile, methacrylonitrile, and ethacrylonitrile. Otherethylenically unsaturated monomers (vinyl monomers) which can be used inaddition to the acrylic monomers include: vinyl aromatic hydrocarbons(such as styrene, alpha-methyl styrene, and vinyl toluene); and vinylaliphatic hydrocarbons (optionally substituted, for example, by halogenatoms) such as vinyl acetate, vinyl versatates, and vinyl chloride.

The vinyl polymerization of the monomer compositions generally can beconducted at from 80° C. to 160° C., and typically are conducted at from100° C. to 150° C.

A vinyl polymerization initiator is employed in the polymerization ofthe vinyl monomer composition(s). Examples of initiators include, butare not limited to: peroxyesters such as tertiary-butyl perbenzoate; azocompounds such as alpha, alpha′-azobis(isobutyronitrile); peroxides suchas benzoyl peroxide and cumene hydroperoxide; peracetates such astertiary butyl peracetate; percarbonates such as isopropyl percarbonate,peroxycarbonates such as butyl isopropyl peroxy carbonate, and similarcompounds. The quantity of initiator employed can be variedconsiderably; however, in most instances, it is desirable to utilizefrom about 0.1 to about 10 percent by weight based on the weight ofethylenically unsaturated monomers used. Where desired, a chainmodifying agent or chain transfer agent can be added to thepolymerization mixture for control of the molecular weight of theresulting resin. Examples of such agents include the mercaptans, such astertiary dodecyl mercaptan, dodecyl mercaptan, octyl mercaptan, andhexyl mercaptan, etc.

The vinyl polymerization reactions for preparing a resin composition ofthe invention generally are carried out in the presence of an organicsolvent, preferably only a limited amount of organic solvent being usedso as to minimize the organic solvent content of the resulting product.In the preferred method of preparing a resin of the invention, the basepolymer serves as a polymerization medium for preparation of themodified polymer thereby significantly reducing the amount of organicsolvent needed. The amount of monomeric materials used for modificationis in the range of about 10% to about 80%, and more preferably, about20% to about 60% based on total modified resin solids. The modifiedpolymer preferably has an acid value of less than 30.

e. Dispersion Process

The production of the dispersions of this invention is effected with adispersing method to incorporate the modified polymer, from section d,into water. In the dispersion process of the present invention, themodified polymer resin is initially liquefied by heating the resin to atleast its melting point, and more preferably, to a temperature of atleast 5° above its melting point so the polymer maintains a molten andflowable state, but below the decomposition temperature of the polymer.Typically, the modified polymer resin will melt in the temperature rangefrom about 120° C. to about 140° C. A separate vessel of water,containing a base for neutralization of the carboxylic acids on thepolymer, is heated to between 20° C. and 70° C. The base can be an aminecompound or an alkali hydroxide. Water solubility or water dilutabilitymay be given to the resin by effecting neutralization of acidic groups,such as carboxyl, with a basic material, e.g. monomethylamine, dimethylamine, trimethylamine, monoethylamine, triethylamine,monoisopropylamine, diisopropylamine, diethylene triamine,triethylenetetramine, monoethanolamine, diethanolamine, triethanolamine,monoisopropanolamine, diisopropanolamine, dimethylethanolamine,morpholine, methyl morpholine, piperazine, ammonia, sodium hydroxide,potassium hydroxide and the like, with or without surfactants. Typicallyenough base is added to neutralize some of the acid on the polymer. Thewater phase and the polymer phase are brought into contact with oneanother and immediately dispersed in a high shear mill or a homogenizer.The high shear is necessary to break the polymer particle down to asub-micron level. Without the use of high shear chopping, the polymerwill not disperse in water. The process can be continuous or in batchmode where the tank or mixing vessel contains the water phase. Once thepolymer is dispersed in water, the pH is adjusted to 7.6–8.2 and thepercent solids are adjusted to 35–55% by weight. Preferably, theresulting polymer dispersion has a volatile organic level of less than10% and an acid number of less than 30.

3. Coating Compositions

The above polymer dispersion can be used by itself as a sole binder, orin combination with a latex as a film forming resin in coatingcompositions.

Examples of latex compositions in which the polymer dispersion productsmay be blended include, for example, those based on resins or binders ofvinyl acrylic, styrene acrylic, all acrylic, copolymers of acrylonitrilewherein the comonomer is a diene like isoprene, butadiene orchloroprene, homopolymers of styrene, homopolymers and copolymers ofvinyl halide resins such as vinyl chloride, vinylidene chloride or vinylesters such as vinyl acetate, vinyl acetate homopolymers and copolymers,copolymers of styrene and unsaturated acid anhydrides like maleicanhydrides, homopolymers and copolymers of acrylic and methacrylic acidand their esters and derivatives, polybutadiene, polyisoprene, butylrubber, natural rubber, ethylene-propylene copolymers, olefins resinslike polyethylene and polypropylene, polyvinyl alcohol, carboxylatednatural and synthetic latexes, epoxies, epoxy esters and other similarpolymeric latex materials. The ratio of the polymers of the presentinvention to the latexes in a coating composition covers a wide rangedepending on the desired properties of the final coating product andintended uses. For example, the product of Section 2.e. of the presentinvention may be present from about 2 weight percent to about 100 weightpercent of the total binder.

The coatings of this invention can be cured oxidatively with metaldriers, or semi-drying oils or fatty acids can be incorporated into theresin. These coatings, whether containing or not containing oxidativemoieties, can also be cured by the addition of crosslinking agents curedeither at room temperature or at elevated temperatures. Metal driers caninclude cobalt, zirconium, or calcium carboxylates, for example.Crosslinking agents can include isocyanates, blocked isocyanates,melamine-formaldehyde resins, urea-formaldehyde resins, aziridines,titanates, carbodiimides, epoxides, epoxy resins, and other crosslinkersknown to those skilled in the art. Aqueous dispersions of theisocyanates, blocked isocyanates, melamine-formaldehyde resins,urea-formaldehyde resins, aziridines, titanates, carbodiimides,epoxides, epoxy resins, and other crosslinkers can also be used.Crosslinking agents can be added to the dispersions of this invention orto blends of these dispersions with latexes or other polymers known toone skilled in the art.

The coatings of this invention may typically be applied to any substratesuch as metal, plastic, wood, paper, ceramic, composites, dry wall, andglass, by brushing, dipping, roll coating, flow coating, spraying orother method conventionally employed in the coating industry.

Opacifying pigments that include white pigments such as titaniumdioxide, zinc oxide, antimony oxide, etc. and organic or inorganicchromatic pigments such as iron oxide, carbon black, phthalocyanineblue, etc. may be used. The coatings may also contain extender pigmentssuch as calcium carbonate, clay, silica, talc, etc.

The following examples have been selected to illustrate specificembodiments and practices of advantage to a more complete understandingof the invention. Unless otherwise stated, “percent” ispercent-by-weight, PVC is pigment volume concentration, NVM isnon-volatile mass, Mn is number average molecular weight, Mw is weightaverage molecular weight, Cps is centipoise, and Pd is polydispersity.

EXAMPLE I Preparation of Low Acid Value Base Polymer—Acidolysis of PET

A 3 liter, 4-necked round bottom flask equipped with inert gas,mechanical stirrer, Barrett tube and Friedrich's condenser is chargedwith 423 grams of polyethylene terephthalate, 822 grams of soya fattyacid, 3.3 grams of dibutyl tin oxide catalyst, and 133 grams ofisophthalic acid. The contents are heated to 490° F. and held until allcontents had melted. The solution is cooled to 325° F. and 206 grams oftrimethylolethane is added. The contents are heated to 460° F. and heldfor an acid value of less than 12. Once reached, heat is removed and thecontents allowed to cool. The final resin product had an NVM of 97.9,viscosity of 12,200 cps (using Brookfield LVT#3 at 25 C., 12 rpm), acidvalue of 6.5, Mw of 3619, Mn of 1639 and Pd of 2.20.

EXAMPLE II Preparation of Low Acid Value Base Polymer—Acidolysis of PET

A 3 liter, 4-necked round bottom flask equipped with inert gas,mechanical stirrer, Barrett tube and Friedrich's condenser is chargedwith 764.72 grams of polyethylene terephthalate, 1124.42 grams of talloil fatty acid, 9.5 grams of dibutyl tin oxide catalyst. The contentsare heated to 490° F. and held until all contents have melted and aclear solution is obtained. The solution is cooled to 325° F. and 301.62grams of trimethylolethane is added. The contents are heated to 465° F.and held for an acid value of less than 10. Once reached, heat isremoved and the contents allowed to cool. The final base polymer resinproduct has an NVM of 98.3, viscosity of 11,200 cps (using BrookfieldLVT#3, 12 rpm), acid value of 6.6, Mz of 4464, Mw of 2522, Mn of 1418and Pd of 1.78.

EXAMPLE III Direct Monomer Modification

511 grams of the resin of Example I and 13 grams of propylene glycolmonobutyl ether are charged in a reaction vessel and heated to about138° C. Added to the vessel over a 3.5 hour period is 333.3 grams ofmethyl methacrylate, 30.2 grams of acrylic acid, and 109.6 grams ofethyl hexyl acrylate. A second feed of 5.7 grams of t-butyl perbenzoate(2.5% in propylene glycol monobutyl ether) is added over the same timeperiod. Upon complete addition of both feeds, a chase of 5.6 gramst-butyl perbenzoate in 10 grams of propylene glycol monobutyl ether isadded over a 1.5 hour time period. Heat is held at 138° C. for one hour.The final monomer-modified polymer had an acid value of 29.

EXAMPLE IV Direct Monomer Modification

600 grams of the base polymer of Example II is charged in a two literflask equipped with condenser, agitator and nitrogen supply. Thecontents are heated to 138° C. and held while the monomer mixturecomprising 37.5 grams acrylic acid, 200 grams methyl methacrylate, 135grams 2-ethylhydroxyacrylate, 200 grams styrene, 8.0 grams t-butylperbenzoate, and 0.72 grams dodecyl mercaptan are added to the basepolymer over three hour period. When monomer addition is complete, thetemperature is held at 138°–140° C. for one hour. After the hold time, amixture of 38.0 grams Acrosolv PNP (available from Lyondell, Houston,Tex.) and 4.5 grams t-Butylperbenzoate is added over a 2.5 hour period,and then held for one half hour at 138° C. to 140° C.

EXAMPLE V Dispersion in Water

The dispersion is produced with a high shear rotor stator mill. Thecomposition of Example III is maintained at 138° C., and is added slowlyto the mill already charged with 1200 grams water and 35 grams oftriethylamine at 70° C. The mixture is mixed until the composition ofExample III is completely incorporated and finely dispersed. Theresulting polymer dispersion is adjusted to have a volatile organiclevel of 5% on solids, NVM of 45%, a pH of 7.8, and a viscosity of 1000cps (Brookfield LVT#3, 30 rpm at 25 C.).

EXAMPLE VI Dispersion in Water

The composition of Example IV is maintained at 138° C., and added slowlyto a high shear rotor stator mill already charged with 1237 grams ofwater and 28 grams of triethylamine at 70° C. The mixture is mixed untilthe composition of Example IV is completely incorporated and finelydispersed, then 27 grams of Pluronic L-62 (available from BASFCorporation, Mt. Olive, N.J.) and 50 grams Igepal CO-997 (Rhodia,Cranberry, N.J.) are added. The dispersion is filtered through 100 meshfilter cloth. The resulting dispersion is adjusted to have NVM of 45.9%,pH of 8.1, and a visocity of 510 cps (Brookfield LVT#3, 30 rpm at 25C.).

EXAMPLE VII Preparation of an Aqueous Coating Composition Using thePolymer Dispersion of Example V as a Secondary Binder

An aqueous coating composition can be prepared as follows. Five grams oftriethylamine and 5 grams of dispersing agent are added to 90 grams ofwater in a stainless steel pot under slow agitation using a grind blade.This is followed by the addition of 210 grams of architectural gradetitanium dioxide, and 5 grams of silicone defoamer. The resulting slurryis ground at high shear (˜3000 rpm) until a Hegman grind of at least 7is obtained. The speed is reduced to ˜1200 rpm, and followed by theaddition of 50 grams of water, and allowed to mix for 5 minutes. Thegrind blade is replaced with a propeller type, mixing blade beforeproceeding to add 22 grams of 2-butoxy ethanol, 445 grams of vinylacrylic latex, and 111 grams of the polymer dispersion (of Example V).This is allowed to mix for 5 minutes before completing the batch with0.5 grams of biocide, 3.5 grams of 5% cobalt hydrocure drier, 1 grams of6% manganese catalyst, and 15 grams of urethane thickener. The final pHis adjusted to a minimum of 9.0 with triethylamine, and the Krebs unitviscosity is adjusted to a range of 97 to 102 with urethane thickener.The resulting coating composition has a PVC of ˜16, a NVM of ˜40, andhas a VOC of less than 120 grams/liter. This coating compositionexhibits excellent wet adhesion properties, and a measured 60° gloss inexcess of 80 units.

EXAMPLE VII Preparation of an Aqueous Coating Composition Using thePolymer Dispersion of Example V as a Sole Binder

Five grams of triethylamine and 5 grams of a dispersing agent are addedto 70 grams of water in a stainless steel pot under slow agitation usinga grind blade. This is followed by the addition of 210 grams of titaniumdioxide and 5 grams of a defoamer, and the resulting slurry ground atabout 3000 rpm until a Hegman grind of at least 7 is obtained. Themixing speed is reduced to about 1500 rpm and followed by the additionof 135 grams of water and mixing for about 5 minutes. The grind blade isreplaced with a mixing blade before proceeding to add 32 grams ofpropylene glycol n-butyl ether, 560 grams of the polymer dispersion (ofExample V), 2.5 grams of 5% Calcium Hydro CEM drier, 1.5 grams of 5%Cobalt Hydrocure II drier, 3.2 grams of 12% Zirconium Hydro CEM drier(all of the above driers available from OMG Inc., Cleveland, Ohio), andProxcel GXL biocide (available from Zeneca, Wilmington, Del.). The finalpH is adjusted to 9.0 with triethylamine, while viscosity is adjusted to95 Krebs Unit using Acrysol RM-825 (available from Rohm & Haas,Philadelphia, Pa.).

EXPERIMENTAL METHODS

Measurement of Gloss:

A drawdown of the test sample on a Leneta WB panel is made with a 4 milgap blade and dried at 25° C./50% relative humidity for 24 hours. Thespecular gloss is measured using a GLOSSGARD II Glossmeter (Byk-Gardner,Silver Springs, Md.) as per ASTM D 523-89 at one of three angles ofreflection, i.e., 20, 60, or 85 degrees.

Measurement of Wet Adhesion:

The panel for the wet adhesion test is a Leneta P121-10N panel that hasbeen coated with gloss polymer and cured for 30 days. 10 mil wet film iscast over the panel at ambient conditions, then the film is allowed todry for 24 hours and then cross-hatched into ¼″ squares, then immersedin water for 30 minutes, followed by scrub machine with wet brush usingLeneta standardized scrub medium SC-2. Results reported as cycles tofailure, or >1000 cycles if 100% of coating remains at 1000 cycles.

Hydrolytic Stability Tests:

The coating is placed in an oven at 140 F., for 4 weeks. Changes toviscosity, pH, and appearance (such as settling, syneresis) are measuredfor the resin as a sole binder and as a latex blend.

Table I shows how blends of latexes perform in the gloss and wetadhesion tests:

TABLE I Wet Primary Ku Gloss Adhesion Ex. Binder Modifier Viscosity pH(60) (Cycles) 1 100% VA None 84 9.5 4 30 2  80% VA 20% WR 83 9.3 31 3 3 80% VA 20% PET 81 9.2 38 150 4  70% VA 30% WR 102 9.4 38 1 5  70% VA30% PET 94 9.2 44 150 6 100% SA NONE 86 9.4 35 >1000 7  80% SA 20% WR 869.3 54 400 8  80% SA 20% PET 90 9.3 66 >1000 9  70% SA 30% WR 84 9.2 65200 10  70% SA 30% PET 108 9.3 81 >1000 VA = Vinyl Acrylic Latex SA =Styrene Acrylic Latex PET = Polyethylene Terephthalate-WaterbornePolymer (Example V) WR = Water Reducible Polymer (Kelsol ® 3922 adjustedto 40% solids from Reichhold Resins)

Table II shows results of hydrolytic stability testing:

TABLE II Primary Ku Gloss Settling/ Ex. Binder Modifier Viscosity pH(60) Syneresis 1 100% VA None  87 9.3  4 None 2  80% VA 20% WR n/a n/an/a Settled 3  80% VA 20% PET  85 9.1 44 None 4  70% VA 30% WR n/a n/an/a Settled 5  70% VA 30% PET  96 9.2 49 None 6 100% SA NONE  89 9.2 32None 7  80% SA 20% WR n/a n/a n/a Settled 8  80% SA 20% PET  94 9.1 69None 9  70% SA 30% WR n/a n/a n/a Settled 10  70% SA 30% PET 102 8.9 84None VA = Vinyl Acrylic Latex SA = Styrene Acrylic Latex PET =Polyethylene Terephthalate-Waterborne Polymer (Example V) WR = WaterReducible Polymer (Kelsol ® 3922 adjusted to 40% solids from ReichholdResins)

1. A process for producing a water-reducible polymer dispersion usefulfor aqueous coating compositions, comprising: (A) producing a modifiedpolymer resin having an acid value less than 30, wherein said modifiedpolymer resin is formed by (1) producing a low acid value polymer formedby reacting (a) a mixture of an acidolysis reaction product of apolyalkylene terephthalate with a member of the group consisting ofacid- and anhydride-functional materials, and (b) an alcohol; whereinthe low acid value polymer has an acid value of less than 20; and (2)performing a monomer modification of the low acid value polymer with anethylenically unsaturated monomer; (B) subjecting the modified polymerresin to temperatures higher than the melting point of the modifiedpolymer resin to maintain the modified polymer resin in a molten andflowable state; (C) combining the molten modified polymer resin withwater in the presence of a base at temperatures sufficient to maintainthe modified polymer resin in a molten state; and (D) forming adispersion of the molten modified polymer resin by subjecting themodified polymer resin to high shear dispersing; and wherein asurfactant is optionally added.
 2. The process of claim 1, wherein atleast one ethylenically-unsaturated monomer is an acid-functionalethylenically-unsaturated monomer.
 3. The process of claim 1, whereinthe acid-functional monomer is at least 5 weight % of the totalethylenically unsaturated monomer present.
 4. The process of claim 1,wherein the polymer dispersion has a volatile organic level of less than10%.
 5. The dispersion of claim 1, wherein for each mole of polyethyleneterephthalate, from about 1.5 to about 4.0 equivalents of acid/anhydrideand from about 2 to about 4 equivalents of hydroxy functionality arepresent.
 6. The process of claim 1, wherein the ethylenicallyunsaturated monomer is in the range of about 10% to about 80% by weightbased on the total weight of the modified resin solids.
 7. The processof claim 1, wherein the surfactant is a non-ionic surfactant.
 8. Aprocess for producing a water-reducible polymer dispersion useful foraqueous coating compositions, comprising: (A) producing a modifiedpolymer resin having an acid value less than 30, wherein said modifiedpolymer resin is formed by (1) producing a low acid value polymer byreacting (a) a mixture of an acidolysis reaction product of apolyalkylene naphthalate with a member of the group consisting of acid-and anhydride-functional materials, and (b) an alcohol, wherein the lowacid value polymer has an acid value of less than 20; and (2) performinga monomer modification of the low acid value polymer with anethylenically unsaturated monomer; (B) subjecting the modified polymerresin to temperatures higher than the melting point of the modifiedpolymer resin to maintain the modified polymer resin in a molten andflowable state; (C) combining the molten modified polymer resin withwater in the presence of a base at temperatures sufficient to maintainthe modified polymer resin in a molten state; and (D) forming adispersion of the molten modified polymer resin by subjecting themodified polymer resin to high shear dispersing; wherein a surfactant isoptionally added.
 9. The process of claim 8, wherein at least oneethylenically-unsaturated monomer is an acid-functionalethylenically-unsaturated monomer.
 10. The process of claim 9, whereinthe acid-functional monomer is at least 5 weight % of the totalethylenically unsaturated monomer present.
 11. The process of claim 8,wherein the polymer dispersion has a volatile organic level of less than10%.
 12. The dispersion of claim 8, wherein for each mole ofpolyalkylene naphthalate, from about 1.5 to about 4.0 equivalents ofacid/anhydride and from about 2 to about 4 equivalents of hydroxyfunctionality are present.
 13. The process of claim 8, wherein theethylenically unsaturated monomer is in the range of about 10% to about80% by weight based on the total weight of the modified polymer resinsolids.
 14. The process of claim 8, wherein the surfactant is anon-ionic surfactant.